<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            position: relative;
            width: 400px;
            border-bottom: 1px solid #ccc;
            margin: 100px auto;
        }
        .box input{
            width: 370px;
            height: 30px;
            border: 0;
            outline: none;
        }
        .box img{
            width: 24px;
            position: absolute;
            top: 8px;
            right: 10px;
        }
    </style>
</head>
<body>
    <div class="box">
    <label for="">
    <img src="./biyan.jpg" id="eye">
</label>
    <input type="password" name="" value="" id="pwd">
    </div>
    <script>
        // 1/获取元素
        var eye = document.getElementById('eye');
        var pwd =  document.getElementById('pwd');
        // 2.注册事件 处理程序
        var flag = 0;
        eye.onclick = function() {
            if(flag == 0){
            pwd.type = 'text';
            flag  = 1;
            eye.src='./zhenyan.jpg';

            }else{
                pwd.type = 'password';
                flag = 0;
                eye.src='./biyan.jpg';
            }
        }
    </script>
</body>
</html>